The invention relates to a self-igniting internal combustion engine.
Self-igniting diesel fueled internal combustion engines of motor vehicles have significantly higher soot emissions compared to gasoline operated internal combustion engines of motor vehicles. Because these soot emissions significantly contribute to fine dust contamination of the air, great efforts are made to lower soot emissions. The same is true for other pollutant emissions of internal combustion engines of motor vehicles such as for example nitrogen oxide emissions. One possibility for lowering pollutant emissions of internal combustion engines is to influence the combustion in the combustion chambers of the cylinders in such a way so as to ensure a complete reaction of the injected fuel with the oxygen in the combustion air into carbon dioxide and water vapor. However, a complete reaction is only possible when fuel and combustion air are well intermixed in the combustion chamber. This intermixing depends inter alia on the geometry of the piston or combustion chamber recess, which is arranged opposite the injector in the front side of the piston.
In order to increase turbulence of the flow of the combustion air inside the piston—or combustion recess and with this the swirling, of the fuel which is injected into the combustion chamber to thereby ensure a better combustion of the fuel, internal combustion engines have previously been proposed in which the piston—or internal combustion recess of the pistons generally has an angled or polygonal contour or circumference. This recess shape is intended to cause turbulences to form in the corners of the piston—or combustion recess, which counteract the main flow or interact with the main flow in other ways in order to ensure a better intermixing of combustion air and fuel due to the forming turbulences.
From DE-A2 343 023, an internal combustion engine of the previously mentioned type is already known in which for improving the distribution and atomization of the injected fuel, the piston—or combustion recess has a generally square contour with rounded corners, while the injector is provided with four injection openings, which are arranged in angular distances of 90 degrees and oriented so that the fuel which is ejected from the injection openings impacts the boundary surface of the piston—or combustion recess before the rounded corners at an oblique angle when viewed in the direction of flow or swirl.
Based on the foregoing, the invention is based on the object to improve an internal combustion engine of the previously mentioned type so that the emissions and in particular the soot emissions of the internal combustion engine can be further decreased.